In the dead of night, just how did the British Air Force manage to gun down German aircraft during World War II? Eating carrots was the key to the pilots’ success, according to the U.K. Ministry of Food. The now-defunct agency rolled out a propaganda campaign detailing the pilots’ superb carrot-enriched night vision and encouraging civilians to devour more of the locally grown vegetable to help them function during blackouts. The root vegetable is rich in beta-carotene, a naturally occurring pigment that nourishes the eye.

Decades later rumors swirled that the British Royal Air Force pushed that message as a cover-up for the recently adopted radar technology they were secretly relying on for their nighttime skirmishes. Information from the de Havilland Aircraft Museum suggests that subterfuge was indeed the British Ministry of Information’s plan. But Bryan Legate, assistant curator at the Royal Air Force Museum in London has a different view. “I would say that whilst the [British] Air Ministry were happy to go along with the story [of carrot-improved vision], they never set out to use it to fool the Germans,” Legate says. “The German intelligence service were well aware of our ground-based radar installation and would not be surprised by the existence of radar in aircraft. In fact, the RAF were able to confirm the existence of German airborne radar simply by fitting commercial radios into a bomber and flying over France listening to the various radio frequencies!” he adds.

Yet the question remains: Are carrots truly able to improve eyesight or is that the stuff of fiction?

The answer is yes, under certain conditions, eating carrots will help improve eyesight.

The body uses beta-carotene to make vitamin A, and “vitamin A is really important, there’s no question about that,” says Emily Chew, deputy clinical director at the National Eye Institute. Vitamin A helps the eye convert light into a signal that can be transmitted to the brain, allowing people to see under conditions of low light. In addition, the cornea (the clear front of the eye) can literally disappear if the body does not get enough vitamin A. Every year an estimated 250,000 to 500,000 children become blind as a result of vitamin A deficiency. In settings where undernourished people suffer from extreme vitamin A deficiencies, such as Nepal or India, supplements of the vitamin or beta-carotene have been shown to improve night vision.

But exactly how many carrots would be needed to optimize night vision remains less clear. Most studies have so far looked at the benefits of beta-carotene or vitamin A supplements, not carrots specifically. One randomized control study in 2005 examined how consumption of roughly 4.5 ounces of cooked carrots six days a week stacked up against other vitamin A–rich options such as fortified rice, amaranth leaf and goat liver for helping address night blindness in pregnant women. The result: all the foods performed roughly the same, although the vitamin A supplement did best of all. The study found that a regular diet of the cooked carrots for six weeks helped to bring women’s response to darkness to normal levels. (In Western nations about 30 percent of dietary vitamin A comes from beta-carotene but in some developing countries it is the sole source of vitamin A.)

Still, other research has shown that beta-carotene does not convert into vitamin A very efficiently—estimates suggest it requires anywhere from 12 to 21 molecules of beta-carotene in the diet to make just one molecule of vitamin A. Beta-carotene, unlike straight vitamin A, would need to be converted in the intestinal wall into vitamin A, meaning most individuals would be better off taking vitamin A supplements, if possible, instead of downing carrots.

Binging on carrots would also not improve most Americans’ eyesight. Once you have enough beta-carotene in your body it often will no longer convert to vitamin A, Chew says. The body naturally regulates against excess amounts of vitamin A to prevent accumulation of toxic levels of the substance. So how many carrots are ideal? “I don’t have any numbers to give you about how many carrots you should eat per day, but everything should be balanced in moderation,” she says. Indeed, if a person eats too many carrots his or her skin may turn a bit orange—a harmless symptom that is not a health concern. Most eye problems stem from vision-impairment caused by issues such as genetics, aging or diabetes that cannot be aided with an infusion of beta-carotene.

The issue of night blindness is far from new. It was detailed in ancient Egyptian texts. The treatment at the time was simple: The juices of a grilled lamb’s liver were squeezed into the eyes of afflicted patients to provide a topical treatment (although the famed ophthalmologist and vitamin A expert Alfred Sommer later wondered if the restoration actually came from perhaps feeding the patients the remaining liver—rich in vitamin A—following such treatments).

When it comes to eating nutrient-rich foods to improve eyesight, more generally, Chew suggests stocking up on green, leafy vegetables. Spinach, kale or collard greens—all chock-full of lutein and zeaxanthin (which are other food-derived nutrients)—could help protect your eyes by filtering high-energy wavelengths of visible light that can damage the retina. Such foods may also help to protect against age-related macular degeneration, the major cause of blindness in the elderly.

ABOUT THE AUTHOR(S)

Dina Fine Maron

Dina Fine Maron is an award-winning journalist and the associate editor for health and medicine at Scientific American. She is also a contributor to the publication's podcasts and Instant Egghead video series. She is based in Washington, D.C.

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